A conventional domestic fan typically includes a set of blades or vanes mounted for rotation about an axis, and drive apparatus for rotating the set of blades to generate an air flow. The movement and circulation of the air flow creates a ‘wind chill’ or breeze and, as a result, the user experiences a cooling effect as heat is dissipated through convection and evaporation. The blades are generally located within a cage which allows an air flow to pass through the housing while preventing users from coming into contact with the rotating blades during use of the fan.
WO 2010/100448 describes a fan assembly which does not use caged blades to project air from the fan assembly. Instead, the fan assembly comprises a base which houses a motor-driven impeller for drawing a primary air flow into the base, and an annular nozzle connected to the base and comprising an annular slot through which the primary air flow is emitted from the fan. The nozzle defines a central opening through which air in the local environment of the fan assembly is drawn by the primary air flow emitted from the mouth, amplifying the primary air flow.
The impeller is in the form of a mixed flow impeller, which receives the primary air flow in an axial direction and emits the primary air flow in both axial and radial directions. The impeller comprises a generally conical hub and a plurality of blades connected to the hub. The impeller is located within an impeller housing mounted within the base of the fan. The leading edges of the blades of the impeller are located adjacent the air inlet of the impeller housing. The leading edges of the blades are rearwardly swept from the impeller hub to the blade tip. In other words, the leading edges of the blades extend rearwardly away from the air inlet of the impeller housing.